Function: break_text

--Usage--
> break_text(some_string, match: regular expression, in_context: regular expression)

Break text by only keeping the parts of the input that match the regular expression.
The function returns a [[type:list]] of parts.

If @in_context@ is given, the context must also match the string where the match is represented as <tt>&lt;match></tt>.

When the @break_text@ is used many times with the same @match@ or @in_context@ values it is more efficient to declare these as default arguments:
> my_break := break_text@(match: "something")
> my_break("input") # called many times
This way the regular expression is only compiled once.

--Filter vs. break--

The function @filter_text@ is very similar to @break_text@, instead of returning a list it concatenates the items.
So for example where @break_text@ returns @["a","b","c"]@, @filter_text@ would return @"abc"@.
In fact, @filter_text@ could be implemented as
> filter_text := { for part in break_text() do part }

--Parameters--
! Parameter	Type			Description
| @input@	[[type:string]]		String to replace in.
| @match@	[[type:regex]]		Regular expression to match.
| @in_context@	[[type:regex]] (optional)	Context to match

--Examples--
> break_text(match: "a",     "banana")  ==  ["a","a","a"]
> break_text(match: "na|.",  "banana")  ==  ["b","a","na","na"]
> break_text(match: "ap",    "banana")  ==  []
> break_text(match: "/",     "a/b/c")   ==  ["/","/"]
> break_text(match: "[^/]+", "a/b/c")   ==  ["a","b","c"]
>
> f := break_text@(match: "xx+")
> f("xyzxxxxyyzz") == ["xxxx"]

--See also--
| [[fun:filter_text]]		Keep only the text matching a regular expression.